The present invention relates to a sample analyzer having a dispensing mechanism for dispensing a reagent or the like.
An automatic analyzer is an apparatus designed to automatize a procedure for mixing a reagent into a sample (specimen), e.g., a bodily fluid such as blood, urine, or cerebrospinal fluid or tissue and performing component analysis and inspection by checking reactions by light. Analysis and inspection can be done in large quantities at once by using this automatic analyzer. Such apparatuses are therefore widely used in hospitals, testing laboratories, and the like, greatly contributing to an improvement in operability.
FIG. 1 shows a general automatic analyzer. General automatic analysis processing will be described below with reference to FIG. 1.
First of all, a sampler 2 rotates by a predetermined amount to move a sample vessel 201 containing a sample as an analysis/measurement target to the position of a sample dispensing mechanism 3. The sample dispensing mechanism 3 aspirates the sample through a probe 31, and discharges the sample in an amount required for analysis processing (required amount) into a reaction vessel 41. Thereafter, a reaction unit 4 further rotates and stops at the position of a reagent dispensing mechanism 7 or 8. The reagent dispensing mechanism 7 or 8 aspirates a reagent used for a measurement item of the sample in the reaction vessel 41 from a reagent reservoir 5 or 6 through a probe 71 or 81, and discharges the required amount of reagent into the reaction vessel 41, thereby executing reagent dispensing. The reaction vessel 41 then moves to the position of an agitating unit 9, so that the mixture of the sample and reagent in the reaction vessel 41 is agitated by an agitating rod 91 of the agitating unit 9. The reaction vessel 41 is analyzed by, for example, a photometer (not shown). After the analysis, the reaction vessel 41 is cleaned by a cleaning mechanism 11 and used for the next sample analysis.
FIGS. 2A, 2B, 2C and 2D are views for explaining one cycle of dispensing operation by the sample dispensing mechanism 3, 7, or 8 shown in FIG. 1. Although FIGS. 2A, 2B, 2C and 2D show a cross-section of the probe 71 of the reagent dispensing mechanism 7 as an example, its arrangement and operation are the same as those of the sample dispensing mechanism 3 or 8.
Dispensing executed by the reagent dispensing mechanism 7 will be described next.
FIG. 2A is a sectional view of the probe 71 before the aspiration of the reagent. FIG. 2B is a sectional view of the probe 71 after the aspiration of the reagent. FIGS. 2C and 2D are sectional view of the probe 71 after the discharge of the reagent.
Referring to FIG. 2A, the probe 71 before the aspiration of the reagent is filled with water 711 that is aspirated in advance. The reagent dispensing mechanism 7 moves up and down and rotates to insert the probe 71 into a reagent vessel 51, and aspirates a predetermined amount of reagent at a predetermined aspiration speed, as shown in FIG. 2B. In FIG. 2B, a measurement reagent 714 is a reagent that is discharged into the reaction unit 4 in an amount required for measurement. An air gap 712 is an air layer that is aspirated before the aspiration of the reagent to prevent the mixing of the reagent with the water. The reagent aspirated as shown in FIG. 2B is discharged as shown in FIG. 2C to be set in the state shown in FIG. 2D. Thereafter, the inside of the probe 71 is cleaned with water 111, and one cycle of reagent dispensing is completed.
In general, when a reagent is aspirated in dispensing, an excess amount 713 of reagent is aspirated as shown in FIG. 2B, in addition to the amount of reagent required for measurement. This operation is performed to compensate for a decrease in reagent concentration due to the mixing of the reagent with the water left on the inner wall of the probe 71.
This reagent aspirated in an excess amount will be referred to as “reagent dummy” hereinafter. In general, the amount of reagent dummy 713 is determined as, for example, <discharge amount×8%+6 μl> in accordance with the amount of reagent discharged. This mathematical expression is applied regardless of the measurement item (the type of reagent). Note that the measurement reagent 714 and reagent dummy 713 are the same, but are illustrated distinct from each other in FIGS. 2A to 2D for the sake of descriptive convenience.
Recently, as a method of decreasing the running cost of the automatic analyzer 1, an attempt has been made to decrease the amount of reagent dummy. In this case, according to a conventional automatic analyzer, the amount of reagent dummy is uniformly decreased from, for example, <discharge amount×8%+6 μl> to <discharge amount×4%+3 μl> regardless of the analysis item or the type of reagent.
Depending on the measurement item (reagent), however, the reagent may scatter or drip from the distal end of the probe 17 when the reagent is discharged, as shown in FIG. 3. This inconvenience occurs because when the amount of reagent dummy is changed, the density and the like vary, and the physical condition for proper dispensing falls outside an allowable range.
Reagents have different components and properties (e.g., surface active effect, viscosity, foaming, and the like). For example, even at the same discharge speed, reagents are basically discharged from the probe in different states depending on their types. Even at a discharge speed at which a given reagent does not foam, another reagent may scatter or drip when they are discharged, or agitation of another reagent and a sample may become insufficient in dispensing operation. As described above, therefore, if the amount of reagent dummy is decreased uniformly regardless of the analysis item or type of reagent, the occurrence of such an inconvenience seems inevitable.
According to the conventional automatic analyzer, factors (e.g., the amount of reagent dummy described above) that determine the physical condition of a reagent in dispensing cannot be defined for each analysis item or each type of reagent. This leads to a low degree of freedom in terms of the use of the apparatus and low compatibility with respect to reagents, as typically indicated by the above reduction in reagent dummy amount.